The magical faeriesword wielded by Arthur, the High King of Albion (or Britan as it was later known) during his reign. Replaced the sword drawn from a stone (which proved his parentage) for differing reasons - some tales say the sword shattered, others that Merlin simply thought he needed a new one. Its scabbard was said to heal any wound, its blade to carve through any foe.

The sword of King Arthur, forged on Avalon (according to Geoffrey), and given to him by the Lady of the Lake to replace the Sword in the Stone (according to Robert de Boron and subsequent writers). It had the magical property of being able to cut through metal and never breaking; but better yet, the shieth made the wearer unable to be injured in battle. When Merlin asked the young Arthur which was better, the sword or the shieth, Arthur answered the sword. Merlin said that this decision would cost the king his life. Morgan le Fay would later steal the scabbard and switch it with a fake one, thus enabling Arthur's mortal wound at Mordred's hand. Excalibur is then said to have been thrown into the lake where it came from, presumably the lake surrounding the Isle of Avalon.

The Irish origin for the name is no mystery; Irish communities settled along the southern coast of Wales from the fifth century onwards; even without this, there was certainly communication and trade between Ireland and Wales. Also, several Irish figures show up in the story "Culhwch and Olwen":

Crychwr the son of Nes, and Cubert the son of Daere, and Percos the son of Poch, and Lluber Beuthach, and Corvil Bervach

He got angry because Arthur asked him to make Guenevere love him. Merlin makes reference to the summoning of the Dragon for Uther who thereby took the shape of the Duke of Cornwall, his castle and his wife, Igrayne (He didn't even bothered taking off his 35kg full plate armour by the way). Cornwall died in the process and Arthur was conceived.
A legend is born.

The team had many adventures, at one point hopping dimensions due to
the actions of a sentient mechanical device called Widget. They
fought such groups as the Technet and Crazy Gang and later
became embroiled in opposing the forces of an black-ops group called
Black Air.